Security sources said the men were being held on suspicion of terrorist activity potentially linked to extremist Islamic beliefs.

Three of the men, of north African origin, were arrested in the Jock's Lodge area of Edinburgh early on Wednesday morning.

The other four were detained in west London and all seven suspects are now being questioned at Govan police station in Glasgow which has high security facilities.

Four properties in Edinburgh were raided

It is understood that the operation was led by the Lothian and Borders Police, assisted by the Metropolitan Police's Anti-Terrorist Branch.

Security sources say that the men are accused of being involved in fund-raising and logistical support, and that they are suspected of being loosely connected to a network associated with al-Qaeda.

However, there has been no evidence that a terrorist attack was being planned.

All those arrested are in their early 30s and have been detained under the Terrorism Act.

Under terrorism legislation the men can be interrogated for 48 hours without being charged, and investigators can then seek permission to continue questioning the suspects.

Officers involved

It is understood that the operation had been several weeks in the planning.

The police presence, which included about 40 vehicles and dozens of officers, began gathering in a shopping centre car park in the Meadowbank area of Edinburgh at about 0130 GMT on Wednesday.

Four different addresses in the Scottish capital were raided.

Police search and forensic teams remained throughout the day at the properties which were raided.

A Metropolitan Police spokesman was unable to say how many officers were involved in the London operation.

He said: "We can confirm that Lothian and Borders Police, assisted by the Metropolitan Police Anti-Terrorist Branch, arrested four men in West London this morning at 6.10am under the Terrorism Act.

There may be no specific threat that we are aware of but there is a general threat here and elsewhere Prime minister's official spokesman

"They have been taken to Scotland to a secure location where they will be interviewed."

Downing Street said it was not aware of any link between the arrests and those made in France earlier this week.

"What it does show is that governments across the world are vigilant to the threat from international terrorism, that we will take whatever action we can to prevent acts of terrorism," said the prime minister's official spokesman.

He said the threat from international terrorism was "very real".

"There may be no specific threat that we are aware of but there is a general threat here and elsewhere," he said.

"And the security services, police and others will continue to do whatever they can to counter that."